Flexible display devices have many advantages, such as impact resistance, high shock resistance, light weight, small volume, and portability. At present, main flexible display materials may be roughly classified into three types: electronic paper (or flexible electrophoretic display), flexible organic light-emitting diodes (OLEDs) and flexible liquid crystals.
A flexible display device comprises a display substrate, which includes a flexible base substrate and a structure located on the flexible base substrate, wherein the flexible base substrate is a polyimide (PI) base substrate, a polyethylene glycol terephthalate (PET) base substrate, or the like; and the structure on the flexible base substrate comprises thin film transistors and insulating layers, and the insulating layers are used for protecting the thin film transistors, so as to prevent the thin film transistors from being damaged when the display substrate is bent. An array substrate of a flexible display device in the prior art usually adopts insulating layers, such as a gate insulating layer, an interlayer insulating layer and a passivation layer. The foregoing insulating layers are generally made of SiNx or SiOx, which causes poor toughness of the insulating layers, and therefore, the insulating layers are apt to fracture when the flexible display device is bent, so that the thin film transistors on the display substrate of the flexible display device are likely to be damaged. For example, as for a thin film transistor (TFT) structure for controlling display of a pixel, accumulation of stress generated when the flexible display device is bent may result in fracture of the insulating layers, which certainly influences performance of the TFT, thereby influencing reliability of the flexible display device and adversely affecting display quality.